Plastics, such as PET, PE, and PP, are commonly used in connection with the manufacture of packaging articles, such as bottles and containers. However, as used herein, “article” shall not be limited to packaging articles. The term “PET” refers to polyethylene terephthalate, and may include its copolymers and combinations. The term “PE” refers to polyethylene, and may include high density polyethylene (“HDPE”), low density polyethylene (“LDPE”), and its copolymers and combinations. The term “PP” refers to polypropylene, and may include its copolymers and combinations. Plastic material, such as PET, can be provided in a number of forms, including flakes and pellets.
PET that is comprised of petrochemical-derived raw materials, or petroleum-based PET, is commonly used to manufacture a number of commercial articles. The cost of petroleum-based PET is, however, closely related to the cost of petroleum. Moreover, as petrochemicals take hundreds of thousands of years to form naturally, petrochemical-derived products are considered to be non-renewable.
Methods for making bio-based plastics, such as bio-based PET packaging, have been disclosed in the art. The term “bio-based” generally refers to the biogenic carbon content of an article, which can be represented as a fraction weight (mass) or percent weight (mass) of the total organic carbon in the article per the ASTM D6866 standard. This standard method can be used to determine precise percentages of a solid, liquid, or gas that came from renewable sources by measuring the material's carbon-14 (C14) content. Since C14 decays at a predictable rate over time (having an approximately 5,000 year half-life) and becomes stable C12 isotope, fossil fuels generally do not contain C14 content due to their age. Thus, the presence of C14 versus C12 in a material can be used to signify/quantify bio-based carbon content. The term “bio-based” can be used to indicate the inclusion of a component that is fully or partially derived from at least one bio-based material, i.e., an organic material in which the associated carbon comes from non-fossil biological sources.
Consumer demand for bio-based plastics, including but not limited to PET, has been on the rise, increasing the need for more productive and efficient means of meeting such demand. Further, many governments, corporations and other organizations have given high priority to developing, finding, subsidizing and using more bio-based products, including plastics. For example, and without limitation, the United States Department of Agriculture has a BioPreferred program that steers contractors towards using more bio-based materials. Average consumers are also becoming more aware of and predisposed to purchasing bio-based products. The sophistication has grown to the point where consumers may, prior to making a purchase, inquire as to the actual bio-based content percentage, recycled content percentage, and/or material types and sources.
For plastic articles, such as containers, including those made from PET, an object can be to economically maximize the bio-based content of the article. Some conventional articles include up to about 30% bio-based content. However, conventional PET containers are not more than one-half bio-based, and commercially available PET containers are not 100% bio-based. Conventional containers with a portion of bio-based content, such as those marketed under the PLANT BOTTLE™ trademark, may employ PET resin having one building block derived from petroleum, and another building block derived from bio-based sources. Specifically, the main components in manufacturing PET via polymerization include terephthalic acid/ester (TA) and ethylene glycol (EG). While the ratios may vary slightly, a typical PET manufacturing process might use about 68.75% TA and about 31.25% EG on a mass basis. Terephthalic acid has eight carbon atoms per molecule, while ethylene glycol has two. The resulting molecule of PET may include 10 total carbon atoms derived from a combination of TA and EG.
Certain bio-based feedstock, including but not limited to sugar cane, sugar beets, or other forms of natural sugar, can be used to produce bio-based EG. The typical process includes converting the feedstock (e.g., via hydro-cracking) into ethylene, adding oxygen to form ethylene oxide, and then adding water to form EG. This process for bio-based EG is similar to that of petrol-based EG, differing primarily in the choice of feedstock and process for converting the feedstock into ethylene. Although generally more expensive and less plentiful than petrol-based EG, bio-based EG is commercially available and is used in some conventional PET resins, for example, those marketed under the PLANT BOTTLE™ name. These resins are said to reach up to 30% bio-based content, derived solely from the bio-based EG component.
A conventional petrol-based process for manufacturing terephthalic acid comprises refining naphtha from crude oil and reforming to paraxylene (pX). The paraxylene is mixed with a solvent (typically acetic acid), catalyst, and promoter and oxidized into crude TA, which may be further refined into purified TA (PTA). Some methods for manufacturing bio-based TA, including those described in U.S. patent application Ser. No. 12/577,480 (Patent Publication No. 2010/0028512), have been proposed.
Further, and without limitation, bio-based polyethylene may be manufactured from 100% bio-based feedstock. A currently available process comprises processing sugar cane or any other form of natural sugar (such as sucrose), fermenting and distilling into ethanol, dehydrating to form ethylene, and then polymerizing to form polyethylene. Such a process can be employed in connection with multiple forms of polyethylene including, without limitation, high density polyethylene (HDPE), linear low density polyethylene (LLDPE), among others. A process associated with forming polypropylene (PP) may be very similar to that associated with forming polyethylene. After forming ethylene, though, the ethylene can be converted to propylene via a dimerization or metathesis process. The propylene monomer may then be converted to polypropylene.
In the pursuit of more eco-friendly packaging, bio-based products, including plastics, are gaining acceptance as potential alternatives to petrol-based products. While certain bio-based plastic materials are known, and may be currently sold in the market, a challenge has been to create an effective means for identifying and recapturing such material in a recycling system.